Estimation of the mechanical property of meniscus using ultrasound: Examinations of native meniscus and effects of enzymatic digestion

Abstract

ABSTRACT:We previously developed a novel ultrasound assessment system featuring wavelet transform to evaluate the material properties of articular cartilage. We aimed in this study to demonstrate the feasibility of quantitative evaluation of meniscus using ultrasound and to elucidate the relationships between its acoustic, mechanical, and biochemical properties. Meniscal disc specimens from mature pigs were assessed by ultrasound and compression testing, and their correlation was analyzed. A positive correlation was found between the ultrasound signal intensity and apparent Young's modulus (r ¼ 0.61). Subsequently, the porcine meniscal discs were treated with various enzymes and then characterized by ultrasound, by compression tests, by biochemical analyses, and by histology and immunohistochemistry. The signal intensity was decreased not by hyaluronidase but by collagenase treatment. Hyaluronidase-treated menisci showed a discrepancy between acoustic and mechanical properties, suggesting that the ultrasound reflection could not detect a reduction in proteoglycan content. Also, ultrasound signal intensity could only reflect superficial layers of the material. Several limitations exist at present, and further studies and improvements of the device are required. However, given the noninvasive nature and the requirement of only small equipment, this ultrasound assessment system will be an instrumental diagnostic tool for meniscal function in both research and clinical fields. ß

Intraoperative Acoustic Evaluation of Living Human Cartilage of the Elbow and Knee during Mosaicplasty for Osteochondritis Dissecans of the Elbow

“…The ultrasound assessment method has been described previously. 8,9,[15][16][17][18][19]34,35 Briefly, the system consists of a transducer and pulser/receiver (Olympus NDT, Tokyo, Japan), a digital oscilloscope, and a personal computer ( Figure 1A). The measurement was done with an acoustic probe with its transducer on the top, and the probe was put perpendicular to the measurement surface.…”

“…8,10 In several animal and human studies, articular cartilage was evaluated using this method. 9,15–18,34,35…”

“…We used an ultrasound assessment method as described previously. 8,9,[15][16][17][18][19]34,35 This method is useful because it evaluates the material properties of articular cartilage quickly and less invasively. We used 3 parameters: signal intensity as an index of cartilage stiffness, signal duration as an index of cartilage roughness, and signal interval as an index of cartilage thickness.…”

“…8,10 In several animal and human studies, articular cartilage was evaluated using this method. 9,[15][16][17][18]34,35 The objective of this study is to evaluate the material properties of cartilage at several different sites in the knee and diseased elbow with our ultrasound assessment. Another objective of this study is to assess the acoustic properties of the cartilage of the transplanted plugs and to compare these plugs with surrounding intact cartilage.…”

Ultrasound has the potential to detect degeneration of articular cartilage clinically, even if the information is obtained from an indirect measurement of intrinsic physical characteristics

“…Our ultimate goal is not to measure the intrinsic physical characteristics but to improve the diagnostic use of an arthroscopic ultrasound system and the method to detect the early stage of degeneration of human articular cartilage. The signal intensity, considering tissue histology [ 4 ] and estimation of the mechanical property of meniscus [ 6 ], was studied aiming toward human clinical study [ 7 ]. Our ultrasound system can be used with the arthroscopic probe and can obtain information on the degeneration of human articular cartilage in vivo .…”